The "defensive strikes" against the Iran-linked Kataib Hezbollah militia group came in response to rocket attacks Friday on an Iraqi base that hosts U.S. coalition forces fighting Daesh.
Three locations in Iraq and two in Syria were targeted, according to chief Pentagon spokesman Jonathan Hoffman.
They included weapon storage facilities and command and control locations which were claimed to be used to plan and carry out attacks on anti-Daesh coalition forces.
The strikes will "degrade" Kataib Hezbollah's "ability to conduct future attacks" against the coalition forces, Hoffman said.
Iran and its Kataib Hezbollah "proxy forces must cease their attacks on U.S. and coalition forces and respect Iraq's sovereignty to prevent additional defensive actions by U.S. forces," Hoffman added.
Meanwhile, the Iraqi militant group Hashd al-Shaabi, an umbrella group for various militia, including Kataib Hezbollah, said in a statement that the airstrikes were conducted by armed U.S. drones.
At least 19 militants were killed and 35 others injured at a Hashd al-Shaabi base located in western Anbar province, according to the militant group.
The military base was the target of a similar attack in August.
On Friday, one U.S. civilian contractor was killed and several U.S. service members and Iraqi personnel were injured in the attack in Iraq’s northern city of Kirkuk.